Thread: Need help with ski??
05-24-2006, 09:58 PM #1
Need help with ski??
I need a little advice on the tuning of my ski. Its a 2002 GP1200. It has the Riva Stage II kit. Also the carbs were sent to IR to be modded and jetted to their specs. (dont know the jetting) I bought this ski used, but I got it from my uncle so I can get answers on specifics if needed. Also running pre-mix fuel and Klotz oil. The ski only has 49 hrs on it. Since i bought it I have added Jims R@D plate, the 05 pump conversion w/14 20, and stepped the stock sponsons. My problem is I am not getting the top speed I am expecting. I have a Tiny Tach reading 6970rpm (but dont how accurate this tach is compared to the PET) which seems low. GPS's around 67. This is with a full tank of gas. Could the carbs be getting gummed up? Im not sure if the winterization was done properly. Are there any additives that can be used to clean them without having to remove them? I have only put 3hrs on the ski since purchased this summer. Also will there be any break in time for the new bearings in the pump?
Future upgades are Ferchos' VF3s, and Jet Works Mod.
Any other suggestions on Mods that I might need???
05-24-2006, 11:27 PM #2
- Join Date
- Jan 2006
- Texas City, Texas
I am not a world class tuner, so keep this in mind.
There is a world of things that could be happening that could cause low rpms, even something as simple as old plugs! But for right now, lets stick to it being a carb issue.
BTW it is not that your tach is inaccurate, it is that it updates slowly, unlike the pet. It is probably fine.
First contact Carl and find his jetting specs to determine that they match your boat (tell him what you have). Ask him where they will eventually wind up once the boat is tuned properly. (More than likely, he set the high and low jet sizes to where the adjustments are about 1 turn out on both your highs and lows, you must confirm this) Ask him if he sends his carbs out adjusted all the way out for safety. More than likely, he sends them out 2 rounds out.
Carl will tell you at what range you should be operating at in terms of high and low adjustment, then you have to find out if you are in that range.
Then ask your uncle if he ever adjusted the carbs properly.
Check your jetting and see where it is. It is very easy to loose 200 rpm if your adjustments are not set right.
What I am saying is don't give up on your carbs so quickly. Bad plugs, a ding in your impeller, jet pump nozzle to small and any combination of these are just a few things that can cause a loss in rpms/speed. Eleminate these sorts of things first before you start tearing into your carbs.
05-25-2006, 08:33 AM #3
The plugs are new. Just put them in. The nozzle is the one Carl recommened for the O5 pump conversion. I would say it was the 85mm. I dont think the carbs were ever adjusted after Carl sent them back. My uncle said he just left them alone...so its possible that they are not adjusted correctly but I dont know much about carb adjustment. I am going to run a compression test just for the sake of knowing. How often do you usually have to re-ring? Im sure the skis are not like the 2-stroke dirtbikes that require it more frequently, but it has 50 hard hrs on it.
05-26-2006, 09:35 PM #4
Spoke with Carl today. He says that the carbs are set up and jetted correctly and should be dailed in really close to where they need to be after they were modded. So unless they are dirty do to poor winterization I am lost at how I could be losing so many RPMs. He recommended tearing the ski apart and returning it to stock and starting over to get baselines and see if i cant find the problem that way. Anybody know anything else I could check??
05-26-2006, 09:49 PM #5
Lets see.....67 on a 1200 riva stage 2 isn't that bad (considering stock speed is about 62).
BUT........you do have a J-Plate and you have upgraded your pump to the 2005 I see, so it is feasable to say that you should be a little faster (but that all depends on your water conditions, mods, humidity and temp as well)
You are getting RPMs that are below 7,000 so that is where i am starting from. Your Tach is accurate like he said above, but i would venture to say that youre boat is having a hard time turning that prop Pitch. (I would upgrade the tach anyway just to see the changes instantly)
You might want to depitch a little because you need to be in the 7150 range on RPMS, so (just thinking outloud) that you might get an extra mile or so by depitching to get in the power band that you need to be in.
You might want to do a compression check on the engine while your at it. I take it that you have the pump sealed and are running a 2-bar grate too since you have the stage 2 right?
05-26-2006, 10:18 PM #6
yeah, I am going to run a compression test tomorrow morning just know what PSI its running.
Also it does have the pump seal kit and the 2 bar grate. Carl seems to think it should be running at least 70 mph. What sucks is i bought the ski used so I dont have baselines to see how it has progressed.
I really hate to have the prop depitched because I would like to get the VF3 cages this summer and this winter during down time I want to send the cylinders off to Lowell to have it ported and get it bored.
Water conditions are really good. I run on the Ohio River and it stays really flat most of the time. The air temp is around 80-85 degrees. Humidity is pretty high.
If it is a compression problem. Any suggestions on new rings? Brands?
Anything else I should have done if I have to tear the ski down?
05-26-2006, 10:23 PM #7If it is a compression problem. Any suggestions on new rings? Brands?
Anything else I should have done if I have to tear the ski down?
If it is a compression problem (which i dont think it really is because i dont think you would be getting the speeds your getting now)--You could use all oem stuff to replace it.
But let me throw this at you -- if your planning in the future to do porting or go bigger bore - you should give Kerry a call. He can help you with the set-up that you are looking for out of it. Lowell is a good one too.
I dont think its an engine issue (but i could be wrong), so if your planning on adding the reeds -then yes you will be right on target with the rpms (should be close). I hope that this helps.
05-26-2006, 10:32 PM #8
Man, thanks for all the help I really appreciate it.
I am planning on getting the reeds, but I want to make sure everything else is in good working order before I do anything else.
I will give Kerry a call.
05-26-2006, 11:35 PM #9
check your powervalves. Unplug the servo motor and open the valves. If you build better rpm's you know that was the problem. Easy and quick to check.
Recheck the gap on the plugs
do a compression test. do the easy things first
05-26-2006, 11:36 PM #10Originally Posted by spud
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